Means for plating stranded cables

ABSTRACT

A stranded cable is passed through a plating bath in a partly slack condition and with some relative mobility of the individual strands. This is accomplished by running the cable in a multiplicity of parallel loops about a driven upper roller above the bath and a submerged lower roller, the latter consisting of a multiplicity of juxtaposed sheaves idling on a shaft. The cable loops are received in confronting grooves of the driven roller and the sheaves, the inner radius of the former decreasing progressively by at least the thickness of the layer deposited on the cable during the preceding immersion.

United States Patent 1 Aseher Nov. 11, 1975 1 MEANS FOR PLATING STRANDED CABLES 143M491 WW4? Erik'sson Cl All. a 1 mole. w inventor: Dieter Ascher, klostcmcuburg 3.3384138 t ll9fi7 Lmdemann 1154A) Austria [T3] Assignee: Firma Karl Neumayer GmbH,

Leobersdorf Austria Filed: Aug. 15, 1972 [ll] Appl. No: 280,833

118/420. DIG. 19

[56] References Cited Primary Iimmim'rTr M Tufariello Attorney. Agent. or Firm-Karl F Ross; Herbert Dubno [57} ABSTRACT A stranded cable is passed through a plating bath in a partly slack condition and with some relati\e mohilit of the individual strands. This is accomplished h running the cable in a multiplicit of parallel loops about a driven upper roller above the hath and a submerged lower roller. the latter consisting of a multiplieit oi 6 Claims 6 Drawing Figures W. e. ...l *l

US. Patent Nov. 11,1975 Sh66t10f3 3,919,069

IIIIII/l/Ill/[II/III/ US. Patent Nov.11, 1975 Sheet20f3 3,919,069

Sheet 3 of 3 U5. Patent Nov. 11, 1975 I l I l I 1 I I I I I I I I I I I I I I I I I I L I I I I l MEANS FOR PLATING STRANDED CABLES My present invention relates to a method of and an apparatus for plating a stranded flexible element, such as a tape or a cable, for the purpose of imparting certain desirable surface characteristics (e.g. corrosion resistance, improved electrical conductivity, or solderability) to the metallic strands thereof.

Heretofore, it has been the practice to coat the strands by electroplating before twisting them into a cable or weaving them into a tape, on the theory that plating of the finished stranded body would be unsatisfactory since the plating bath whould have only limited access to the surface of that body at points where its strands are in contact with one another. Such prior plating of the strands, however. is disadvantageous in that a much greater length of metallic filament must be passed through the treatment bath than if the stranded element itself were subjected to the plating process. Moreover, the galvanically deposited coating may be damaged during the twisting or weaving process, thereby detracting from the metallurgical, physical or electrical properties sought to be imparted thereto.

1 have found that the prejudice of persons skilled in the art against the plating of stranded bodies is due to the fact that such bodies. if elongated. are generally subjected to considerable tension on being guided through the bath, this tension being indeed the cause of close contact between the strands and relative immobilization thereof which makes uniform coating impossible. Thus, the object of my present invention is to provide an improved system for solving this problem in the plating of stranded elements.

This object is realized, pursuant to my present invention, by leading the stranded element (referred to hereinafter simply as *cable") through a plating bath in a sufficiently slack state to facilitate relative motion of its individual strands, such relative motion being imparted to the strands during their passage through the bath by subjecting the cable to varying tension or flexure.

Changing the curvature of the immersed cable, as by guiding it into and out of the bath in a downwardly elongated loop or a series of such loops, causes a certain relative shifting of adjacent strands; also, if the loops are allowed to hang slack, there will be no transverse pressure preventing such relative motion. As a result, all surface portions of each strand will be exposed atone time or another to the treatment fluid and will be substantially uniformly coated with the metal dissolved therein.

An apparatus designed to guide the cable in this manner comprises one or more upper rollers above the bath level, driven by a common motor, and a corresponding number of nondriven lower rollers submerged in substantial vertical alignment with respective upper rollers, the cable passing in a multiplicity of successive loops around the two rollers of each pair. Positive guidance for the cable may be provided by peripherally grooving each roller, the submerged roller advantageously consisting of a multiplicity of juxtaposed sheaves idling on a common shaft. In order to allow for the progressive increase in thickness as the cable dips into the bath in the lower part of each loop, the inner radius of the grooves of at least one set (preferably those of the upper roller) decreases progressively in the direction of successive engagement by the cable; the decrease from one groove to the next should be at least 2 equal to the thickness of the layer deposited on the cable during the preceding immersion.

For electrochemical deposition. the cable must be cathodically connected in an electric circuit also including an anode immersed in the bath. To insure the safety of the operating personnel during the initial looping of the cable around the rollers, these rollers are advantageously carried on an elevatable mounting allowing the lower roller or rollers to be lifted out of the bath with simultaneous disconnection ofthe cable from its current supply.

The multiple winding of the cable around the driven upper roller insures that the cable will be entrained even if friction between it and the roller surface is low, i.e., if the cable is under very low tension. The relative mobility of the several sheaves of the lower roller prevents the development of local stresses during the treatment.

Tin. silver and other metals can be deposited on the stranded cable in this manner. For the usual type of electric wiring. the strands may be copper filaments ranging between 0.05 and 0.03 mm in thickness; thus. for example, I8 strands of 0.l mm thickness or 26 strands of 0.2 mm thickness could be twisted together to form a thinner or a heavier cable. The strands could also be wound around a nonconductive core. e.g. of synthetic resin. For other purposes the strands may consist of such less electrically conductive metals as aluminum or iron to be subjected, for example, to a galvanizing (zinc-plating) treatment. Stranded elements so treated may also be used as conductive sheaths for insulated conductors, e.g. in coaxial cables. antenna leads, waveguides and the like.

The above and other features of my invention will be described in detail hereinafter with reference to the accompanying drawing in which:

FIG. 1 is a somewhat diagrammatic cross-sectional view, taken on the line l] of FIG. 1, of an apparatus for electroplating a stranded cable in accordance with this invention;

FIG. 2 is a cross-sectional view taken on the line llll of FIG. 1;

FIG. 3 is a top plan view of the apparatus shown in FIGS. l and 2;

FIG. 4 is a perspective view of a length of cable to be treated by the apparatus of FIGS. 1-3;

FIG. 5 is a view similar to FIG. 4, showing a modified cable; and

FIG. 6 is a diagrammatic cross-sectional view of another apparatus for carrying out the process according to my invention.

In FIGS. 1-3 I have shown an apparatus for electroplating a cable 9 consisting of twisted metallic strands 31 (e.g. of 0.] mm diameter) as illustrated in FIG. 4. The apparatus comprises a series of upwardly open receptacles 18 (for a degreasing solution), 19 (for a rinsing liquid), 20 (for an electroplating bath) and 21 (for another rinse). Each of these four treatment stages comprises at least one upper roller 2, 2a, 2b, 2c. 2d (the two rollers 2b and 2c lying above the plating bath 1 in tank 20), disposed horizontally above the respective receptacle, and a corresponding number of lower rollers vertically aligned with the respective upper rollers. One such lower roller, associated with upper roller 2b. has been shown at I] in FIGS. 1 and 2. It comprises a multiplicity of sheaves l3 idling on a shaft 25 which is rotated by a drive motor 10 through the intermediary of a transmission 5. This motor also drives the several 3 upper rollers through respective speed reducers. some of which have been shown at 6, 6b. and 6t; shaft 25 up crates a propeller l which serves to agitate the plating bath l and which could also be duplicated on the nonillustratcd lower rollers associated with upper rollers 2, 2a, 21' and 2d. Sheaves 13 have peripheral grooves l4 which are substantially in line with similar annulargrooves l2 on upper roller 2b; the grooves 12 and 14 form guide channels for the cable 9 which is led around the rollers in a multiplicity of downwardly elongated loops as best seen in FIG. 2. Shaft 25. a drive shaft 26 for roller 2b and similar drive shafts for all the other rollers are journaled in an elevatable structure which includes a hollow beam 17 with depending tubular arms 22. the latter accommodating the transmission elcments for the lower rollers. Arm 22 also supports a frame 27 with horizontal rods 27. 27 which spread the loops sideways to keep them from assuming a concave shape as illustrated in dot-dash lines in FIG. 2; such inversion of curvature could be detrimental to the metallic coating by causing excessive flexural stresses. It will be noted, however. that even the bulging loops maintained by the spreader frame 27 experience a distinct change in curvature below the bath level so that the cable 9 is flexed to a varying extent and. by virtue ofits slack state. undergoes a certain relative shifting of its strands. Rods 27 and 27 may be provided with eyes of rubber or the like serving to wipe adherent liquid from the cable.

In the ease of roller 2!). oncoming cable 9 is first received in the outermost groove 12 at the free end of that roller and then progressively moves inward; in the case of roller 20 the movement is reversed. The diame ter of roller 21). and with it the inner radius of its grooves 12, decreases progressively from its free end inward. the diameter and groove radius of roller 21' de creasing outwardly toward the free end. The reduction in diameter from one groove to the next may amount. for example. to 0.03 mm.

The mounting structure 17, 22 is supported on a vertical hydraulic jack l6 enabling the lifting of the lower rollers above the liquid level in their respective treat ment tanks. When this occurs. a conductive connection extending from the metallic upper roller 2h through its shaft 26 to a source of positive voltage(+) is broken by the disengagement of a collar 28 on the shaft from a brush 23 whose base rests on a stationary bracket 24 secured to tank 20. Thus. the cable is disconnected from high voltage at the time of such elevation and can be safely threaded onto or removed from the rollers.

It will be noted that rollers 20 and 2d above the rinsing compartments are axially narrower than rollers 2, 2b and 2c; otherwise, their construction as well as that of the associated lower rollers may be the same as that of rollers 2b and ll described in detail above. except for the absence of a taper.

In FIG. 5 l have shown a modified cable 9 wherein the strands 3] form a sheath above a central conductor 29 with interposition ofinsulation 30. The strands here are interwoven. rather than twisted as in cable 9.

FIG. 6 shows a vessel 120 wherein a cable 9 is guided over upper rollers 102. 102a and lower rollers Ill,

lllu under intermittent tension from a motor-driven roller 103 about which the cable has been wound several times. Roller I03 has an eccentric profile so that the cable 9 is alternately slackcned and stressed. This action. too. causes a limited relative motion of the strands in the electroplating bath 101. It will be understood that in this case. likewise. the high-voltage connection to the workpiece 9 may be automatically interrupted upon a lifting ofthe rollers 11]. lllu out ofthe bath.

I claim:

l. An apparatus for plating a stranded flexible element. comprising a vessel adapted to contain a plating bath up to a predetermined level. upper roller means above said level in said vessel provided with a first set of axially spaced peripheral annular groves, lower rol ler means below said level in said vessel provided with a second set of axially spaced annular grooves substantially aligned with the grooves of said first set for guiding an element to be plated in a multiplicity of parallel. slack loops into and out of the bath. and drive means coupled with said upper roller means for advancing said element through said vessel; the radius of the grooves of at least one of said sets progressively decreasing. in the direction of successive engagement by said element. by at least an amount corresponding to the thickness of a coating deposited thereon in a preceding immersion in the bath.

2. An apparatus as defined in claim 1 wherein said driven roller means comprises a roller tapering in said direction of successive engagement.

3. An apparatus as defined in claim I wherein said upper and lower roller means are provided with a common mounting elevatable to raise said second guide means above said level. further comprising an energizing circuit for cathodically connecting said element during passage through the bath. said circuit including contacts on said mounting opened upon elevation thereof.

4. An apparatus for plating a stranded flexible element. comprising a vessel adapted to contain a plating bath up to a predetermined level, a roller above said level in said vessel provided with a first set of axially spaced peripheral annular grooves. a shaft in said vessel carrying a multiplicity ofjuxtaposed and independently rotatable sheaves idling thereon below said level. said sheaves being provided with a second set of peripheral annular grooves substantially aligned with the grooves of said first set for guiding an element to be plated in a multiplicity of parallel. slack loops into and out of the bath, and drive means coupled with said roller for advancing said element through said vessel.

5. An apparatus as defined in claim 4 wherein the inner radius of the grooves of at least one of said sets progressively decreases in the direction of successive engagement by said element by at least an amount corresponding to the thickness of a coating deposited thereon in a preceding immersion in the bath.

6. An apparatus as defined in claim 5 wherein said driven roller tapers in said direction of successive engagement. 

1. AN APPARATUS FOR PLATING A STRANDED FLEXIBLE ELEMENT, COMPRISING A VESSEL ADAPTED TO CONTAIN A PLATING BATH UP TO A PREDETERMINED LEVEL, UPPER ROLLER MEANS ABOVE SAID LEVEL IN SAID VESSEL PROVIDED WITH A FIRST SET OF AXIALLY SPACED PERIPHERAL ANULLAR GROVES, LOWER ROLLER MEANS BELOW SAID LEVEL IN SAID VESSEL PROVIDED WITH A SECOND SET OF AXIALLY SPACED ANNULAR GROOVES SUBSTANTIALLY ALIGNED WITH THE GROOVES OF SAID FIRST SET FOR GUIDING AN ELEMENT TO BE PLATED IN A MULTIPLICITY OF PARALLEL, SLACK LOOPS INTO AND OUT OF THE BATH, AND DRIVE MEANS COUPLED WITH SAID UPPER ROLLER MEANS FOR ADVANCING SAID ELEMENT THROUGH SAID VESSEL, THE RADIUS OF THE GROOVES OF AT LEAST ONE OF SAID SETS PROGRESSIVELY DECREASING, IN THE DIRECTION OF SUCCESSIVE ENGAGEMENT BY SAID ELEMENT, BY AT LEAST AN AMOUNT
 2. An apparatus as defined in claim 1 wherein said driven roller means comprises a roller tapering in said direction of successive engagement.
 3. An apparatus as defined in claim 1 wherein said upper and lower roller means are provided with a common mounting elevatable to raise said second guide means above said level, further comprising an energizing circuit for cathodically connecting said element during passage through the bath, said circuit including contacts on said mounting opened upon elevation thereof.
 4. An apparatus for plating a stranded flexible element, comprising a vessel adapted to contain a plating bath up to a predetermined level, a roller above said level in said vessel provided with a first set of axially spaced peripheral annular grooves, a shaft in said vessel carrying a multiplicity of juxtaposed and independently rotatable sheaves idling thereon below said level, said sheaves being provided with a second set of peripheral annular grooves substantially aligned with the grooves of said first set for guiding an element to be plated in a multiplicity of parallel, slack loops into and out of the bath, and drive means coupled with said roller for advancing said element through said vessel.
 5. An apparatus as defined in claim 4 wherein the inner radius of the grooves of at least one of said sets progressively decreases in the direction of successive engagement by said element by at least an amount corresponding to the thickness of a coating deposited thereon in a preceding immersion in the bath.
 6. An apparatus as defined in claim 5 wherein said driven roller tapers in said direction of successive engagement. 